Power storage devices have recently attracted attention and found practical use as backup power sources for commercial power sources. In a case where a commercial power source operates normally, a backup power source is charged, and when the commercial power source fails, the backup power source continues to supply power, in place of the commercial power source, to a device. A UPS (Uninterruptible Power Supply) is an example of such a system. When the commercial power supply stops, a network device such as a computer, a memory device, or a server that is being used is prevented from stopping by instantaneous switching to power supply from the backup power source.
In a backup power source combined with such a power storage device, control is performed so as to maintain a high residual capacity indicating a state of charge of the power storage device (referred to hereinbelow as “SOC”). Typically in such an elevator system, because the excess power is efficiently charged into the power storage device by a power generation action of a motor, charge control is performed so that the SOC does not increase to 100%. Furthermore, because the power is supplied to the motor when necessary, discharge control is performed to prevent the SOC from dropping to 0 (zero). More specifically, the control is usually performed to maintain the SOC of the power storage device within a range of 20 to 80%.
A hybrid elevator has been developed by providing an elevator with a vehicle cage and a counterweight, so that power consumption necessary during the operation is inhibited. In the hybrid elevator, where an abnormal state such as a stop occurs during operation, by using the power of the power storage device, it is possible to supply the power for driving the elevator from the power storage device, move the elevator to the nearest floor or any floor, and safely rescue the passengers located in the cage. For example, Patent Document 1 discloses a method by which an output voltage, an output current, and a temperature of a battery power source are detected and a rescue operation corresponding to a power supply capacity of the battery power source is performed as a control method for an automatic reach-a-floor device of the elevator.
With a known method for calculating a power supply capacity of a power source device that is used in the above-described backup power source, the power supply capacity is typically calculated from an open voltage, an inner resistance, and a minimum voltage of the power source device, as shown by the following Equation (1).Power Supply Capacity=Minimum Voltage×(Open Voltage−Minimum Voltage)/Inner Resistance  (1)
A method for calculations from the open voltage, inner resistance, and maximum voltage of the power source, as shown by Equation (2) below, is known as a method for calculating the electric power regeneration capacity.Electric Power Regeneration Capacity=Maximum Voltage×(Maximum Voltage−Open Voltage)/Inner Resistance  (2)
The minimum voltage and maximum voltage that are used when calculating the power supply capacity and electric power regeneration capacity are set with a certain margin with consideration for the service life of the power source device.
With the method disclosed in Patent Document 1, the output voltage value and voltage set value of the power source device are compared correspondingly to the discharge time, the discharge state of the battery is detected by the relationship between the two values, and the operation of elevator is controlled. Therefore, in a case, where the power supply capacity of the battery power source is small, the power supply capacity is zeroed, and power supply from the battery is terminated. A problem encountered in this case is that because the charge to the battery power source is started after the operation of the power source device is restored and the rescue operation is performed after the charge is completed, the rescue operation to the nearest floor usually cannot be performed when a failure of the power source occurs, and the passengers are locked up in the elevator.
Furthermore, in order to enable minimum operations to ensure safety and reliability in a case where the power source device stops due to an accident, as in the case of a hybrid elevator, a minimum necessary power supply capacity is required for the backup power source. As a result, a margin is necessary for the capacity of the power source device that is used in the backup power source and a large power source device is required.
The minimum voltage and maximum voltage that are used when the power supply capacity and electric power regeneration capacity of the power source device are calculated have a margin determined with consideration for a service life characteristic of the power storage device. Therefore, actual power supply capacity and electric power regeneration capacity assume values that are less than those of the original power supply capacity and electric power regeneration capacity of the power source device.
Patent Document 1: Japanese Patent Application Laid-open No. 11-199152